lx8585.pdf

LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
KEY FEATURES
DESCRIPTION
ƒ Three Terminal Adjustable or
Fixed Output
ƒ Guaranteed < 1.2V headroom
@ 4.6A (LX8585A)
ƒ Guaranteed < 1.4V headroom
@ 4.6A (LX8585)
ƒ Guaranteed < 1.3V Headroom
@ 3A
ƒ Output Current of 4.6A
Minimum
ƒ Fast Transient Response
ƒ 1% Voltage Reference Initial
Accuracy
ƒ Output Short Circuit Protection
ƒ Built-In Thermal Shutdown
bs
ol
et
e
short-circuit current. On-chip thermal
limiting provides protection against any
possible overload that would create
excessive junction temperatures. The
LX8585/85A family is available in both
through-hole
and
surface-mount
versions of the industry standard 3-pin
TO-220 / TO-263 power packages.
The
LX1431
Programmable
Reference and LX8585A Series
products offer precision output voltage
and are ideal for use in VRE
applications (see application below).
For higher current applications, see the
LX8584 data sheet.
APPLICATIONS
Pentium Processor Supplies
Power PC Supplies
Microprocessor Supplies
Low Voltage Logic Supplies
Battery Powered Circuit
Post Regulator for Switching
Supply
ƒ CYRIX® 6x86™ Supplies
ƒ AMD-K5™ Supplies
ƒ
ƒ
ƒ
ƒ
ƒ
ƒ
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
PRODUCT HIGHLIGHT
THE A PPLICATION OF THE LX8585A & LX1431 IN A
75 & 166 MHZ P54C P ROCESSORS USING 5V CACHE
3
5V
WWW . Microsemi .C OM
The LX8585/85A Series ICs are
low dropout three-terminal regulators
with a minimum of 4.6A output
current. Pentium® Processor and
Power PCTM applications requiring
fast transient response are ideally
suited for this product family. The
LX8585A is guaranteed to have <
1.2V at 4.6A, while the LX8585 are
specified for 1.4V, making them ideal
to provide well regulated outputs of
2.5V to 3.6V using a 5V input supply.
Fixed versions are also available and
specified in the Available Options
table below. Current limit is trimmed
above 4.6A to ensure adequate output
current and controlled
VIN
VO 4.6A
(See Table Below)
2
VOUT
LX8585A
Part
2x
330 µ F, 6.3V
Low ESR
Oscon Type
from Sanyo
1k Ω
ADJ
1k Ω
1
0.01 µF
100 µ F x 6
10V
AVX TYPE
TPS
250pF
1
2
3
220 µF
10V
Low ESR
from Sanyo
1k
COL
V+
REF
LX1431
Part
0.1 µF
50V
SGND
0.1%
8
2.84k Ω
0.1%
Available Options Per Part Number
Part #
Output Voltage
LX8585/85A-00
Adjustable
LX8585/85A-15
1.5V
LX8585/85A-33
3.3V
µP
Load
Other voltage options may be available.
Please contact factory for details.
21k
1%
1 µ F x 10
SMD
JP1
FGND
6
O
5
PLACE IN µP SOCKET CAVITY
VOUT
3.50
3.38
JP1
Short
Open
Typical Application
120 / 166MHz, VRE, 5V Cache
75/90/100/133MHz, STND, 5V Cache
LX8585
Thick traces represent high current traces which must be low resistance / low inductance
traces in order to achieve good transient response.
PACKAGE ORDER INFO
TA (°C)
Dropout
Voltage
0 to 125
1.4V
1.2V
P
Plastic TO-220
3-Pin
DD
Plastic TO-263
3-Pin
RoHS Compliant
Transition DC: 0543
RoHS Compliant
Transition DC: 0535
LX8585-xxCP
LX8585A-xxCP
LX8585-xxCDD
LX8585A-xxCDD
Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX8585-15CDD-TR)
Copyright © 1997
Rev. 2.2a, 2005-11-10
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
ABSOLUTE MAXIMUM RATINGS
PACKAGE PIN OUT
TAB is GND
3
VIN
2
VOUT
1
ADJ/GND*
P PACKAGE
(Top View)
TAB is GND
3
VIN
2
VOUT
1
ADJ / GND*
bs
ol
et
e
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to
Ground. Currents are positive into, negative out of specified terminal.
THERMAL DATA
WWW . Microsemi .C OM
Power Dissipation ....................................................................................Internally Limited
Input Voltage .................................................................................................................10V
Input to Output Voltage Differential..............................................................................10V
Maximum Operating Junction Temperature .............................................................. 150°C
Storage Temperature Range.........................................................................-65°C to 150°C
Peak Package Temp. for Solder Reflow (40 seconds max. exposure)............ 260°C (+0 -5)
DD PACKAGE
P
(Top View)
PlasticTO-220 3-Pin
THERMAL RESISTANCE-JUNCTION TO TAB, θJT
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
DD
3.0°C/W
60°C/W
* Pin 1 is GND for fixed voltage versions
RoHS 100% Matte Tin Lead Finish
Plastic TO-263 3-Pin
THERMAL RESISTANCE-JUNCTION TO TAB, θJT
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
3.0°C/W
60°C/W
Copyright © 1997
Rev. 2.2a, 2005-11-10
PACKAGE DATA
O
Junction Temperature Calculation: TJ = TA + (PD x θJA).
The θJA numbers are guidelines for the thermal performance of the device/pc-board system. All of the
above assume no ambient airflow.
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 2
LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
ELECTRICAL CHARACTERISTICS
Parameter
`
Symbol
Min
70°C except where
LX8585/85A
Typ
Max
Units
LX8585-00 / 8585A-00 (ADJUSTABLE)
Reference Voltage
IOUT = 10mA, TA = 25°C
10mA < IOUT < 4.6A, 1.5V < (VIN – VOUT), VIN < 7V,
P < PMAX
∆VREF(VIN) IOUT = 10mA, 1.5V < (VIN – VOUT), VIN < 7V
VREF(IOUT) VIN – VOUT = 3V, 10mA < IOUT < 4.6V
∆VOUT (Pwr) TA = 25°C, 20ms pulse
VOUT = 3.3V, f = 120Hz, COUT = 100µF Tantalum,
VIN = 5V, CADJ = 10µF,
TA = 25°C, IOUT = 4.6V
IADJ
10mA < IOUT < 4.6A, 1.5V < (VIN – VOUT),
∆IADJ
VIN < 7V
∆VREF = 1%, IOUT = 4.6A
∆V
∆VREF = 1%, IOUT = 3A
∆VREF = 1%, IOUT = 4.6A
IOUT(MIN)
VIN < 7V
IOUT(MAX)
1.4V < (VIN – VOUT), VIN < 7V
∆VOUT(t)
∆VOUT(t)
TA = 125°C, 1000hrs
VREF
1.238
1.250
1.262
1.225
1.250
1.275
0.035
0.1
0.01
0.20
0.5
0.02
V
bs
ol
et
e
Line Regulation (Note 2)
Load Regulation (Note 2)
Thermal Regulation
Ripple Rejection (Note 3)
Adjust Pin Current
Adjust pin Current Change
Dropout Voltage
LX8585
LX8585A
`
Test Conditions
≤
Minimum Load Current
Maximum Output Current (Note 4)
Temperature Stability (Note 3)
Long Term Stability (Note 3)
RMS Output Noise
(% of VOUT)(Note 3)
LX8585-15 / 8585A-15 (1.5V FIXED)
Output Voltage (Note 4)
Line Regulation (Note 2)
Load Regulation (Note 2)
Thermal Regulation (Note 3)
Ripple Rejection (Note 3)
Quiescent Current
Dropout Voltage
LX8585-15
VOUT
VOUT(RMS)
83
55
TA = 125°C, 10Hz < f < 10kHz
VIN = 5V, IOUT = 0mA, TA = 25°C
4.75 < VIN < 10V, 0mA < IOUT < 7A, TA = 25°C, P
< PMAX
4.75 < VIN < 7V
∆VOUT (VIN)
4.75V < VIN < 10V
∆VOUT(IOUT) VIN = 5V, 10mA < IOUT < IOUT(MAX)
∆VOUT(Pwr) TA = 25°C, 20ms pulse
COUT = 100µF (Tantalum), IOUT = 4.6A,
TA = 25°C
IQ
0mA < IOUT < IOUT(MAX), 4.75V < VIN < 10V
∆VOUT = 1%, IOUT < IOUT(MAX), VIN - VOUT < 7V
∆V
∆VOUT = 1%, IOUT < 3A, VIN - VOUT < 7V
∆VOUT = 1%, IOUT < IOUT(MAX), VIN - VOUT < 7V
∆VOUT(T)
∆VOUT(t)
TA = 125°C, 1000hrs
O
LX8585A-15
Temperature Stability (Note 3)
Long Term Stability (Note 3)
RMS Output Noise (% of
VOUT)(NOTE 3)
VOUT(RMS)
60
µA
0.2
5
µA
1.2
1.1
1.1
2
4.6
0.25
0.3
1.4
1.3
1.2
10
6
1
1.485
1.50
1.515
1.470
1.50
1.530
1
1
2.5
0.01
3
5
7
0.02
TA = 25°C, 10Hz < f < 10kHz
dB
100
0.003
65
%
%
%/W
83
4
1.2
1.1
1.1
0.25
0.3
0.003
10
1.4
1.3
1.2
1
V
mA
A
%
%
%
V
mV
mV
%/W
dB
mA
V
%
%
%
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
ELECTRICALS
Note 2: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating
effects are covered under the specification for thermal regulations.
Note 3: These parameters, although guaranteed, are not tested in production.
Note 4: IOUT(MAX) is measured under the condition that VOUT is forced below its nominal value by 100mV.
Copyright © 1997
Rev. 2.2a, 2005-11-10
WWW . Microsemi .C OM
Unless otherwise specified, the following specifications apply over the operating ambient temperature 0°C ≤ TA
otherwise noted and the following test conditions:.
Page 3
LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
APPLICATION CIRCUITS
VIN
IN
10µF
LX8585/85A
OUT
ADJ
R1
121Ω
1%
R2
365 Ω
1%
VOUT
VIN
IN
(Note A)
150 µF
C1
10µF*
LX8585/85A
OUT
ADJ
C1*
10µF
VOUT**
R1
121Ω
R2
1k
C2
100µF
bs
ol
et
e
* C1 improves ripple rejection.
X C should be ≈ R1 at ripple
frequency.
5V
Figure 1 – Improving Ripple Rejection
Needed if device is far from filter capacitors.
WWW . Microsemi .C OM
(Note A)
** VOUT = 1.25V 1 + R2
R1
Figure 2 – 1.2V – 8V Adjustable Regulator
LX8585/85A
OUT
IN
ADJ
VIN
(Note A)
5V
121Ω
1%
100µF
10µF
1k
TTL
Output
2N3904
1k
365Ω
1%
Figure 3 – 5V Regulator With Shutdown
LX8585-33/85A-33
IN
OUT
GND
10µF Tantalum
or 100µF Aluminum
3.3V
Min. 15µF Tantalum or
100µF Aluminum capacitor.
May be increased without
limit. ESR must be less
than 50mΩ.
APPLICATIONS
O
VIN
Figure 4 – Fixed 3.3V Output Regulator
Note A: VIN(MIN) = (Intended VOUT) + (VDROPOUT(MAX))
Copyright © 1997
Rev. 2.2a, 2005-11-10
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 4
LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
APPLICATION NOTE
IN
LX8585/85A
OUT
ADJ
Minumum Load
(Larger resistor)
Full Load
(Smaller resistor)
RDSON<< RL
1 sec
Star Ground
10ms
Figure 5 – Dynamic Input & Output Test
Output
15µF Tantalum, 100µF Aluminum
47µF Tantalum, 220µF Aluminum
Adj
None
15µF
O
To ensure good transient response from the power supply system
under rapidly changing current load conditions, designers
generally use several output capacitors connected in parallel. Such
an arrangement serves to minimize the effects of the parasitic
resistance (ESR) and inductance (ESL) that are present in all
capacitors. Cost effective solutions that sufficiently limit ESR and
ESL effects generally result in total capacitance values in the
range of hundreds to thousands of microfarads, which is more than
adequate to meet regulator output capacitor specifications. Output
capacitance values may be increased without limit.
The circuit shown in Figure 5 can be used to observe the
transient response characteristics of the regulator in a power
system under changing loads. The effects of different capacitor
types and values on transient response parameters, such as
overshoot and undershoot, can be compared quickly in order to
develop an optimum solution.
Copyright © 1997
Rev. 2.2a, 2005-11-10
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 5
APPLICATIONS
OVERLOAD RECOVERY
Like almost all IC power regulators, the LX8585/85A regulators
are equipped with Safe Operating Area (SOA) protection. The
SOA circuit limits the regulator's maximum output current to
progressively lower values as the input-to-output voltage
difference increases. By limiting the maximum output current, the
SOA circuit keeps the amount of power that is dissipated in the
regulator itself within safe limits for all values of input-to-output
voltage within the operating range of the regulator. The
LX8585/85A SOA protection system is designed to be able to
supply some output current for all values of input-to-output
voltage, up to the device breakdown voltage.
Under some conditions, a correctly operating SOA circuit may
prevent a power supply system from returning to regulated
operation after removal of an intermittent short circuit at the
output of the regulator. This is a normal mode of operation which
can be seen in most similar products, including older devices such
as 7800 series regulators. It is most likely to occur when the
power system input voltage is relatively high and the load
impedance is relatively low.
When the power system is started “cold”, both the input and
output voltages are very close to zero. The output voltage closely
follows the rising input voltage, and the input-to-output voltage
difference is small. The SOA circuit therefore permits the
regulator to supply large amounts of current as needed to develop
the designed voltage level at the regulator output.
Now consider the case where the regulator is supplying
regulated voltage to a resistive load under steady state conditions.
A moderate input-to-output voltage appears across the regulator
but the voltage difference is small enough that the SOA circuitry
allows sufficient current to flow through the regulator to develop
the designed output voltage across the load resistance. If the
output resistor is short circuited to ground, the input-to-output
voltage difference across the regulator suddenly becomes larger
by the amount of voltage that had appeared across the load
resistor. The SOA circuit reads the increased input-to-output
voltage, and cuts back the amount of current that it will permit the
regulator to supply to its output terminal. When the short circuit
across the output resistor is removed, all the regulator output
current will again flow through the output resistor. The maximum
current that the regulator can supply to the resistor will be limited
by the SOA circuit, based on the large input-to-output voltage
across the regulator at the time the short circuit is removed from
the output.
bs
ol
et
e
Input
10µF
10µF
Power Supply
WWW . Microsemi .C OM
The LX8585/85A Series ICs are easy to use Low-Dropout
(LDO) voltage regulators. They have all of the standard selfprotection features expected of a voltage regulator: short circuit
protection, safe operating area protection and automatic thermal
shutdown if the device temperature rises above approximately
165°C.
Use of an output capacitor is REQUIRED with the LX8585/85A
series. Please see the table below for recommended minimum
capacitor values.
These regulators offer a more tightly controlled reference voltage
tolerance and superior reference stability when measured against
the older pin-compatible regulator types that they replace.
STABILITY
The output capacitor is part of the regulator’s frequency
compensation system. Many types of capacitors are available, with
different capacitance value tolerances, capacitance temperature
coefficients, and equivalent series impedances. For all operating
conditions, connection of a 220μF aluminum electrolytic capacitor
or a 47μF solid tantalum capacitor between the output terminal
and ground will guarantee stable operation.
If a bypass capacitor is connected between the output voltage
adjust (ADJ) pin and ground, ripple rejection will be improved
(please see the section entitled “RIPPLE REJECTION”). When
ADJ pin bypassing is used, the required output capacitor value
increases. Output capacitor values of 220μF (aluminum) or 47μF
(tantalum) provide for all cases of bypassing the ADJ pin. If an
ADJ pin bypass capacitor is not used, smaller output capacitor
values are adequate. The table below shows recommended
minimum capacitance values for stable operation
LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
APPLICATION NOTE
IN
VIN
LX8585/85A
OUT
ADJ
WWW . Microsemi .C OM
VOUT
VREF
R1
IADJ
50µA
R2
VOUT = VREF 1 + R2 + I ADJ R2
R1
bs
ol
et
e
OVERLOAD RECOVERY (continued)
If this limited current is not sufficient to develop the designed
voltage across the output resistor, the voltage will stabilize at some
lower value, and will never reach the designed value. Under these
circumstances, it may be necessary to cycle the input voltage
down to zero in order to make the regulator output voltage return
to regulation.
RIPPLE REJECTION
Ripple rejection can be improved by connecting a capacitor
between the ADJ pin and ground. The value of the capacitor
should be chosen so that the impedance of the capacitor is equal in
magnitude to the resistance of R1 at the ripple frequency. The
capacitor value can be determined by using this equation:
C = 1 / (6.28 * FR * R1)
where: C ≡ the value of the capacitor in Farads; select an equal
or larger standard value.
FR ≡ the ripple frequency in Hz
R1 ≡ the value of resistor R1 in ohms
⎛ R2 + R1 ⎞
⎟
⎝ R1 ⎠
R Peff = R P * ⎜
where: RP ≡ Actual parasitic line resistance.
When the circuit is connected as shown in Figure 7, the parasitic
resistance appears as its actual value, rather than the higher RPeff
IN
LX8585/85A
OUT
ADJ
R1
O
VIN
RP
Parasitic
Line Resistance
R2
Connect
R1 to Case
of Regulator
RL
Connect
R2
to Load
Figure 7 – Connections For Best Load Regulation
Copyright © 1997
Rev. 2.2a, 2005-11-10
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 6
APPLICATIONS
At a ripple frequency of 120Hz, with R1 = 100Ω:
C = 1 / (6.28 * 120Hz * 100Ω) = 13.3μF
The closest equal or larger standard value should be used, in this
case, 15μF.
When an ADJ pin bypass capacitor is used, output ripple
amplitude will be essentially independent of the output voltage. If
an ADJ pin bypass capacitor is not used, output ripple will be
proportional to the ratio of the output voltage to the reference
voltage:
M = VOUT/VREF
where: M ≡ a multiplier for the ripple seen when the ADJ pin is
optimally bypassed.
VREF = 1.25V.
For example, if VOUT = 2.5V the output ripple will be:
M = 2.5V/1.25V= 2
Output ripple will be twice as bad as it would be if the ADJ pin
were to be bypassed to ground with a properly selected capacitor.
OUTPUT VOLTAGE
The LX8585/85A ICs develop a 1.25V reference voltage
between the output and the adjust terminal (See Figure 6). By
placing a resistor, R1, between these two terminals, a constant
current is caused to flow through R1 and down through R2 to set
the overall output voltage. Normally this current is the specified
minimum load current of 10mA. Because IADJ is very small and
constant when compared with the current through R1, it represents
a small error and can usually be ignored.
Figure 6 – Basic Adjustable Regulator
LOAD REGULATION
Because the LX8585/85A regulators are three-terminal devices,
it is not possible to provide true remote load sensing. Load
regulation will be limited by the resistance of the wire connecting
the regulator to the load. The data sheet specification for load
regulation is measured at the bottom of the package. Negative
side sensing is a true Kelvin connection, with the bottom of the
output divider returned to the negative side of the load. Although
it may not be immediately obvious, best load regulation is
obtained when the top of the resistor divider, (R1), is connected
directly to the case of the regulator, not to the load. This is
illustrated in Figure 7. If R1 were connected to the load, the
effective resistance between the regulator and the load would be:
LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
APPLICATION NOTE
can be used, as long as its added contribution to thermal
resistance is considered. Note that the case of all devices in this
series is electrically connected to the output.
Copyright © 1997
Rev. 2.2a, 2005-11-10
TJ
TC
R
JT
TS
R
TA
R
CS
SA
First, find the maximum allowable thermal resistance of the heat
sink:
R ΘSA =
(
TJ − TA
PD
− (R ΘJT + R ΘCS )
)
PD = VIN(MAX) − VOUT I OUT = (5.0V − 2.8V) * 5.0A
= 11.0W
R ΘSA =
125°C − 50°C
(5.0V − 2.8V) * 5.0A
− (2.7°C/W + 1.0°C/W)
= 3.1°C/W
Next, select a suitable heat sink. The selected heat sink must
have RΘSA < 3.1°C/W. Thermalloy heatsink 6296B has RΘSA =
3.0°C/W with 300ft/min airflow.
Finally, verify that junction temperature remains within
specification using the selected heat sink:
APPLICATIONS
O
bs
ol
et
e
Example
Given: VIN = 5V
VOUT = 2.8V, IOUT = 5.0A
Ambient Temp. TA = 50°C
RΘJT = 2.7°C/W for TO-220
300 ft/min airflow available
Find:
Proper Heat Sink to keep IC’s junction temperature
below 125°C.**
Solution: The junction temperature is:
TJ = PD (RΘJT + RΘCS + RΘSA) + TA
Where: PD ≡ Dissipated Power
RΘJT ≡ Thermal resistance from the junction to the
mounting tab of the package
RΘCS ≡ Thermal resistance through the interface
between the IC and the surface on which it is mounted.
(1.0°C/W at 6 in-lbs mounting screw torque).
RΘSA ≡ Thermal resistance from the mounting surface
to ambient (thermal resistance of the heat sink).
TS ≡ heat sink temperature.
WWW . Microsemi .C OM
LOAD REGULATION (continued)
Even when the circuit is configured optimally, parasitic
resistance can be a significant source of error. A 100 mil (2.54
mm) wide PC trace built from 1 oz. copper-clad circuit board
material has a parasitic resistance of about 5 milliohms per inch of
its length at room temperature. If a 3-terminal regulator used to
supply 2.50 volts is connected by 2 inches of this trace to a load
which draws 5 amps of current, a 50 millivolt drop will appear
between the regulator and the load. Even when the regulator
output voltage is precisely 2.50 volts, the load will only see 2.45
volts, which is a 2% error. It is important to keep the connection
between the regulator output pin and the load as short as possible,
and to use wide traces or heavy-gauge wire.
The minimum specified output capacitance for the regulator
should be located near the regulator package. If several capacitors
are used in parallel to construct the power system output
capacitance, any capacitors beyond the minimum needed to meet
the specified requirements of the regulator should be located near
the sections of the load that require rapidly-changing amounts of
current. Placing capacitors near the sources of load transients will
help ensure that power system transient response is not impaired
by the effects of trace impedance.
To maintain good load regulation, wide traces should be used on
the input side of the regulator, especially between the input
capacitors and the regulator. Input capacitor ESR must be small
enough that the voltage at the input pin does not drop below VIN
(MIN) during transients.
VIN (MIN) = VOUT + VDROPOUT (MAX)
where: VIN (MIN) ≡ the lowest allowable instantaneous voltage at
the input pin.
VOUT ≡ the designed output voltage for the power supply
system.
VDROPOUT (MAX) ≡ the specified dropout voltage for the
installed regulator.
THERMAL CONSIDERATIONS
The LX8585/85A regulators have internal power and thermal
limiting circuitry designed to protect each device under overload
conditions. For continuous normal load conditions, however,
maximum junction temperature ratings must not be exceeded. It is
important to give careful consideration to all sources of thermal
resistance from junction to ambient. This includes junction to case,
case to heat sink interface, and heat sink thermal resistance itself.
Junction-to-case thermal resistance is specified from the IC
junction to the back surface of the case directly opposite the die.
This is the lowest resistance path for heat flow. Proper mounting is
required to ensure the best possible thermal flow from this area of
the package to the heat sink. Thermal compound at the case-to
heat-sink interface is strongly recommended. If the case of the
device must be electrically isolated, a thermally conductive spacer
TJ = 11W(2.7°C/W + 1.0°C/W + 3.0°C/W) + 50°C = 124°C
**Although the device can operate up to 150°C junction, it is
recommended for long term reliability to keep the junction
temperature below 125°C whenever possible.
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 7
LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
PACKAGE DIMENSIONS
WWW . Microsemi .C OM
P
3-Pin Plastic TO-220
B
S
F
T
Q
MILLIMETERS
MIN
MAX
14.22
15.88
9.65
10.67
3.56
4.83
0.51
1.14
3.53
4.09
2.54 BSC
6.35
0.30
1.14
12.70
14.73
1.14
1.27
5.08 TYP
2.54
3.05
2.03
2.92
1.14
1.40
5.84
6.86
0.508
1.14
INCHES
MIN
MAX
0.560
0.625
0.380
0.420
0.140
0.190
0.020
0.045
0.139
0.161
0.100 BSC
0.250
0.012
0.045
0.500
0.580
0.045
0.050
0.200 TYP
0.100
0.120
0.080
0.115
0.045
0.055
0.230
0.270
0.020
0.045
bs
ol
et
e
U
Dim
A
B
C
D
F
G
H
J
K
L
N
Q
R
S
T
U
A
1
2
C
3
H
R
K
D
Note:
L
1. Dimensions do not include mold flash or protrusions;
these shall not exceed 0.155mm(.006”) on any side.
Lead dimension shall not include solder coverage.
J
G
Copyright © 1997
Rev. 2.2a, 2005-11-10
MECHANICALS
O
N
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 8
LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
PACKAGE DIMENSIONS
3-Pin Plastic TO-263
I
A
D
Dim
A
B
C
D
E
F
G
H
I
J
K
M
N
C
MILLIMETERS
MIN
MAX
10.03
10.67
8.51
9.17
4.19
4.59
1.14
1.40
0.330
0.51
1.19
1.34
2.41
2.66
2.29
2.79
–
1.65
0
0.25
14.60
15.87
7°
3°
INCHES
MIN
MAX
0.395
0.420
0.335
0.361
0.165
0.181
0.045
0.055
0.013
0.020
0.047
0.053
0.095
0.104
0.090
0.110
–
0.065
0
0.010
0.575
0.625
7°
3°
bs
ol
et
e
B
K
M
N
H
F
WWW . Microsemi .C OM
DD
E
G
Note:
0° -8°
1. Dimensions do not include mold flash or protrusions; these
shall not exceed 0.155mm(.006”) on any side. Lead
dimension shall not include solder coverage.
J
Copyright © 1997
Rev. 2.2a, 2005-11-10
MECHANICALS
O
Seating Plane
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 9
LX8585-xx / LX858A-xx
®
TM
4.6A Low Dropout Positive Regulators
P RODUCTION D ATA S HEET
NOTES
O
bs
ol
et
e
WWW . Microsemi .C OM
NOTES
PRODUCTION DATA – Information contained in this document is proprietary to
Microsemi and is current as of publication date. This document may not be modified in
any way without the express written consent of Microsemi. Product processing does not
necessarily include testing of all parameters. Microsemi reserves the right to change the
configuration and performance of the product and to discontinue product at any time.
Copyright © 1997
Rev. 2.2a, 2005-11-10
Microsemi
Integrated Products Division
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 10